Well, Tim is not entirely right about the Libelle wings.
They ALL have a balsa shear web in the spar. Glasflugel
did phase out the use of balsa as a core material in
skins. To see the progression, go to:

http://www.streifly.de/home-eng.html

Select the tab for 'Technical Info', then follow your
way through to the Tech Notes Summary for the 201 Libelle.
You can download the summary and most of the specific
tech notes as .pdfs. Very handy to put into a notebook
for reference.

The Reader's Digest Version is that PVC Foam replaced
balsa in the core of the wing skins from serial number
111 and on. Balsa was removed from the aileron skins
from serial 113 and up. From the rudder serial 160
and up. Serial 182 and higher got a new airfoil for
the horizontal tail, foam instead of balsa in the fin,
and removal of the balsa from the elevator. The dive
brakes change was effective serial 120 and up. I do
not see mention of a bigger horizontal tail, but I
know the early ones had a much thinner tail airfoil
section with a much sharper leading edge. All this
info is available at the above referenced website.

I do agree with Tim that if it has been nicely taken
care of, it will be an excellent machine. Regardless
of how much balsa is in the skins. I have never gotten
to fly a Libelle, but I have a couple of other Glasflugel
sailplanes, and they are wonderful flying machines.
I am looking forward to getting to stuff myself into
a Libelle some day. But, I like flaps, so mine will
likely be a 301 Libelle.

Steve Leonard
Wichita, KS

Steve Leonard wrote:
> Well, Tim is not entirely right about the Libelle wings.
> They ALL have a balsa shear web in the spar. Glasflugel
> did phase out the use of balsa as a core material in
> skins. To see the progression, go to:
>
> http://www.streifly.de/home-eng.html
>
> Select the tab for 'Technical Info', then follow your
> way through to the Tech Notes Summary for the 201 Libelle.
> You can download the summary and most of the specific
> tech notes as .pdfs. Very handy to put into a notebook
> for reference.
>
> The Reader's Digest Version is that PVC Foam replaced
> balsa in the core of the wing skins from serial number
> 111 and on. Balsa was removed from the aileron skins
> from serial 113 and up. From the rudder serial 160
> and up. Serial 182 and higher got a new airfoil for
> the horizontal tail, foam instead of balsa in the fin,
> and removal of the balsa from the elevator. The dive
> brakes change was effective serial 120 and up. I do
> not see mention of a bigger horizontal tail, but I
> know the early ones had a much thinner tail airfoil
> section with a much sharper leading edge. All this
> info is available at the above referenced website.
>
> I do agree with Tim that if it has been nicely taken
> care of, it will be an excellent machine. Regardless
> of how much balsa is in the skins. I have never gotten
> to fly a Libelle, but I have a couple of other Glasflugel
> sailplanes, and they are wonderful flying machines.
> I am looking forward to getting to stuff myself into
> a Libelle some day. But, I like flaps, so mine will
> likely be a 301 Libelle.
>
Thanks for the reference and summary, Steve.

Mine is s/n 82 and so this confirms what I had thought - its balsa all
through. I had wondered, too, what was in the spars and thought it might
be balsa from the sheer cross section of the stubs. If the comment that
"any 201 can be retrofitted with a B stamp" is really true, my guess is
that anything after s/n 120 resembles what is commonly known as an
H-201B - all foam skins and top surface brakes.

Mine has had the Streifeneider go-faster treatment: full span zigzag
turbs on the wing under surface and mylar control gap seals. It seems to
have gained a point or two as a result.


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